Change User Password in Windows XP

Click Start - Control Panel - User Accounts
Select the Account
Click 'Change my password'
Enter the details
Click Change Password


You can also change password from disk management.

Right click 'My Computer' icon on desktop, select Manage
or
Click Start - Control Panel - Administrative Tools - Computer Management
Expand 'Local Users and Groups'
Click Users
Select the user on right hand side, right click & Select 'Set Password'
Click Proceed
Enter the password & confirm it.
Click OK